Black garlic: A number of chemical processes transform this humble ingredient during aging. For instance, the garlic picks up caramel notes during browning. Hints of dried fruit come out. And natural microbes on the garlic bulb can ferment, creating more distinct flavors.

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Originally published on June 24, 2016 4:35 pm

There's an explosion of interest in friendly bacteria.

Beneficial microorganisms, as we've reported, can help us digest food, make vitamins, and protect us against harmful pathogens.

As this idea gains traction, so too does the popularity of fermented foods such as yogurt, sauerkraut and kimchi.

Though the science is tricky, researchers are learning more about how this ancient technique for preserving food may also promote good health.

For instance, the bacteria in yogurt have been shown to aid digestion, and making cabbage into sauerkraut by fermenting it "increases glucosinolate compounds believed to fight cancer," explains a Tufts University Health & Nutrition publication.

So, what's next in fermentation? Chefs and do-it-yourself enthusiasts are using microorganisms to coax new, complex flavors out of foods.

"Cooks around the world have begun to discover (or, more accurately, to rediscover) the possibilities of using fermentation processes in the kitchen," writes Arielle Johnson, a flavor chemist, in an article titled "Artisanal Food Microbiology" published in Nature Microbiology this spring.

Johnson works for MAD, a nonprofit food organization based in Copenhagen that was founded by Rene Redzepi, the chef-patron of the acclaimed restaurant Noma.

Fermentation, she explains, is loosely defined as the transformation of food by microorganisms. "When you ferment something, you create flavour," Johnson writes.

Food is biologically transformed by the bacteria and other microorganisms that live in or on it. "In general, a pool of larger-molecular-weight, and usually less flavor-active molecules ... are transformed into a more diverse group of tastier, smaller molecules, such as amino acids, organic acids, esters ... and aromatic compounds," Johnson explains.

As more chefs experiment with microorganisms "to transform ingredients and create new flavors," fermentation has gone from preservation technique to culinary tool — one that's "every bit as essential as a paring knife or frying pan," Johnson argues.

In addition to the innovations at Noma in Copenhagen, Johnson points to kitchens around the world, such as Sean Brock's restaurant Husk in Charleston, S.C., Momofuku in New York, and Bar Tartine in San Francisco, that are experimenting with these techniques.

During the spring, he fermented ramps to make a ramp kimchi and made an exquisite black garlic aioli.

If you listen to the audio of my conversation with David Greene on Morning Edition, you'll hear Weland describe how he transformed a simple bulb of garlic into something extraordinary. (Hint: The garlic cooks at low heat in a humid environment for six to eight weeks.) "What comes out, [the] flavors, works wonders," Weland told us.

During this aging, a number of chemical processes transform this humble ingredient. For instance, the garlic picks up caramel notes during browning. Hints of dried fruit come out. Also, natural microbes on the garlic bulb can ferment, creating more distinct flavors.

"I'm a huge fan of black garlic," chef Dan Barber of Blue Hill told me. "We serve it with vegetables mostly." Barber says he's made his own, but he also imports black garlic from Japan, where it's marketed under the name Fruit Garlic of Japan. It's "insanely good," Barber says.

So, as chefs catch the bug, academics are elevating fermentation to a higher level, too. For instance, there's now a fermentation certificate program at the University of Wisconsin-Milwaukee.

And, at the Culinary Institute of America in Hyde Park, N.Y., there's a new focus on the fermented product that has perhaps the widest appeal in our culture: beer. The school now offers an elective course, the art and science of brewing, taught in the newly built brewery on campus.

Students are taught the basics of brewing, with a focus on science. "I would say the most exciting development has been the ready use of wild yeast and bacteria in beer fermentation," says Hutch Kugeman, head brewer at the CIA.

Using wild yeast and bacteria "allows a range of really interesting flavors in beers, from the tart lemon of lactobacillus to the funky barnyard aromas of brettanomyces," Kugeman says.

So it seems from chefs to brewers, foodies are turning to microorganisms to amp up flavor.

If you'd like to try this at home, check out DIY sites or a fermentation festival. Sandor Katz, a fermenting enthusiast and author of The Art of Fermentation, keeps fellow enthusiasts in the loop.

Copyright 2017 NPR. To see more, visit http://www.npr.org/.

DAVID GREENE, HOST:

And we've been talking a lot about food on MORNING EDITION recently. NPR's Allison Aubrey is back here. And Allison, last time you and I were talking about eggs.

ALLISON AUBREY, BYLINE: Yes.

GREENE: You gave me permission to put cheese in my eggs...

AUBREY: That's right.

GREENE: ...Which was the best news I've ever gotten in my life. And so I'm very excited about what you are talking about here, now.

AUBREY: All right, so I think today, David, we are going to talk flavor...

GREENE: Awesome.

AUBREY: ...Old flavors that are new again. And...

GREENE: Oh, that's poetic.

AUBREY: ...I'm going to be making the case that we need to get to know these flavors. I'm going to start by persuading you. So will you do me a favor and...

GREENE: Anything you want.

AUBREY: ...Taste something?

GREENE: Yeah, anything you want.

AUBREY: OK, brought this for you...

GREENE: You got a Crock-Pot.

AUBREY: Any idea what this is?

GREENE: No, it doesn't look appetizing.

AUBREY: OK, in fact...

GREENE: Oh, it looks like burnt garlic cloves.

AUBREY: It's so ugly that...

GREENE: Gosh.

AUBREY: ...When I had this on my desk, the cleaning crew threw it away.

(LAUGHTER)

GREENE: So when some - when the cleaning crew tries to throw something away, is your immediate reaction let me bring this to David so he can eat it?

AUBREY: (Laughter) Pretty much so.

GREENE: OK, awesome.

AUBREY: But really, check this out. I've got - describe, what do you see? What do you think it is?

GREENE: This is the inside of a garlic with - I mean, it's the kind of garlic you would sort of squish together and put on a salad but it's burned...

AUBREY: So you think it's garlic.

GREENE: ...But it's burned. It's, like, burned.

AUBREY: You think it's garlic...

GREENE: I do.

AUBREY: ...But give it a taste.

GREENE: All right, I'm going to...

AUBREY: There's a little clove for you.

GREENE: OK - oh.

AUBREY: Surprise, right?

GREENE: It's sort of gum texture.

AUBREY: When I first tasted it, I was blown away. It hit me like dried fruit.

GREENE: It's not terrible. It is sort of like dried fruit.

AUBREY: Almost like a date.

GREENE: Uh huh, kind of surprising - is it garlic?

AUBREY: Well, actually, six weeks ago it was a garlic, and now it's been transformed into something completely new. You taste all those, like, layers of flavor. Like, to me, there was this whole bouquet of taste. There were, like, little bits of cherry, fig. It has this, like, molasses quality...

GREENE: Yeah...

AUBREY: ...A little nuttiness...

GREENE: ...It's still in my mouth right now. It lasts.

AUBREY: So the origins of this - it's called a black garlic...

GREENE: OK.

AUBREY: ...Go back to Asia, so Korea, Japan. It's millennia old. It's long been touted as something that's good for your health. And it's just starting to show up here in the U.S. starting about five years ago...

GREENE: But let's be clear. This is just 6-week-old garlic? It becomes this after sitting there and aging all this time?

AUBREY: And you're about to get to see the process.

GREENE: Oh, nice.

AUBREY: I'm about to bring you into the process here.

GREENE: I'm ready.

AUBREY: I got turned onto this by a chef here in Washington. His name is Rob Weland. And he's turned a little part of his kitchen at Garrison restaurant into this chemistry lab I visited. And you've got to imagine - it's this modern, sleek Capitol Hill restaurant. But in the back of the house, he took me to this dark little corner where he's got jars of all kinds of things fermenting. And he's got this little oven where he slow cooks these cloves of garlic for weeks. So he showed me the process.

ROB WELAND: So this is essentially the beginning stages of the garlic. It'll sit in there for six to eight weeks probably. And yeah, what comes out is an amazing product.

GREENE: Slow cooking for six weeks, like it's literally cooking for six weeks?

AUBREY: That's right. And when it does that, there's this, like, whole cascade of chemical reactions going on so creating entirely new flavors. I mean, this does not taste like a garlic, right?

GREENE: No, and it has the consistency of, like, a Swedish Fish. I mean...

AUBREY: Right.

GREENE: ...It's - but tastes better. It tastes better.

AUBREY: Right, and some of these flavors in here are kind of funky. So when you heat the garlic, here you get this browning effect, similar to what you get when you brown meat.

GREENE: Right.

AUBREY: So you get that, like, nice caramelization and probably some of that texture you're talking about.

GREENE: Yeah.

AUBREY: And then there's also a kind of fermentation happening because there's all these little microbes in the air and on the garlic here when the process starts. Now, this is kind of complicated. So I reached out to Matt Hartings. He's a food science professor at American University. And he tells me this is one of the most ancient ways of creating flavor.

MATT HARTINGS: In my romantic mind, I kind of imagine it being sort of like the first fermentations where someone left fruit juice out and some yeast got into it, you know, so...

AUBREY: And said, aha, wine.

HARTINGS: ...Yeah, and aha, wine 30 days later. And something like this - they took some garlic, and they put it in a warm place, forgot about it, came back to it a month later and aha, black garlic.

GREENE: This guy's very excited about fermentation.

AUBREY: Well, he's excited about the idea that could have been a mistake - right? - discovering this thousands of years ago.

GREENE: Yeah.

AUBREY: But, you know, the thing is we don't even realize how many foods get their distinctive flavors from fermentation. So I've got a goodie bag for you right there, David.

GREENE: Yeah, this is...

AUBREY: You want to open that up?

GREENE: I would love to.

AUBREY: All right, tell us what's in there.

GREENE: This is all stuff that gets better with age. Is that right?

AUBREY: That's the theme here, yeah.

GREENE: OK, I have - oh, this is kosher for Passover - or is that just the jar?

AUBREY: It's sauerkraut (laughter).

(LAUGHTER)

GREENE: OK, sauerkraut, good, then we have a bottle of red blend California wine.

AUBREY: So all of these foods are really being - you can think of it as being transformed by the power of friendly microbes. These microbes set off little chemical reactions that create new compounds and new flavors. So the microbes are actually changing the taste of these things. And the bonus really is is that these compounds, some of them, can be really good for our health. Our bodies can really benefit from a lot of this good bacteria.

GREENE: Bacteria's a good thing.

AUBREY: Well, you know, you hear eat more yogurt.

GREENE: Right.

AUBREY: You hear about kimchi being a health food. This field of research is really exploding.

GREENE: Why now? I mean, didn't people always know that, like, cheese tasted better when it was aged? Is this...

AUBREY: Well, I think...

GREENE: ...Something people are into, trying aging different things?

AUBREY: I think the enthusiasm for fermented foods comes at a time when we're learning just how important all of the bacteria that live in us and on us and around us are. I mean, this is called the microbiome. Here's Matt Hartings again.

HARTINGS: In science, the microbiome is really hot right now. It's a really hot topic. And the president just announced the Microbiome Initiative. So our bodies are covered in bacteria, and so our foods are the same way, right? And we live in this symbiosis with microbes around us.

GREENE: So microbes create new flavor. And, I mean, you said, like, when they discovered that wine tasted good when aged was kind of a surprise. Could - I mean, could I start testing stuff in my own kitchen and age it and ferment it and see if something weird happens?

AUBREY: (Laughter) That's right. I mean, what's happening is people know that these microorganisms can create flavor. So they're playing with this and rediscovering things like black garlic which has been around for millennia. Now, all you need to do, David, if you want to make this is pop it in here for six weeks, let it sit, low heat.

GREENE: It is something really different. But it does leave an aftertaste like garlic does...

AUBREY: You know what...

GREENE: It's definitely still there, I...

AUBREY: ...What I recommend is that you kind of, like, spread it on a piece of bread...

GREENE: Oh, not eat it in a chunk like you gave it to me.

AUBREY: No, when chefs use it, they kind of blend it in with a plate of vegetables so you don't necessarily have to sit and munch on the whole clove...